The present invention refers to a filling pipe for use in a filling machine for filling sacks or bags, especially valve sacks, and refers in particular to a filling pipe of the type having a ring chamber which is in fluid communication with an air conduit.
A conventional filling pipe is provided on one end with a connection flange for attachment to the filling machine, with the outlet opening of the filling pipe situated on the opposite end of the connection flange. German patent no. DE 38 34 810 A1 describes a filling pipe which allows admittance of pressurized air via the air conduit into the ring chamber after withdrawing the valve sack from the filling pipe for cleaning the filling pipe. Suitably, the filling pipe has a perforated forward portion or a forward portion in form of a wire fabric, with the ring chamber being spaced from the free end of the filling pipe.
This conventional filling pipe has the drawback that the valve sack cannot be filled sufficiently accurate with a predetermined desired weight since material trickles out after termination of the filling process, thus adversely affecting the weight accuracy. Moreover, subsequently outflowing material not only contaminates the filling machine but is also annoying to the operating personnel. It was thus proposed to equip the conventional filling pipe with a suction hood.
In order to avoid a trickling out of material, German patent no. DE 38 07 254 C1 describes the attachment of a tubular body inside the filling pipe, with both ends of the tubular body being secured to the filling pipe. The tubular body is acted upon by pressurized air and made of elastically deformable material. After stopping the filling process, pressurized air is admitted to push the tubular body together from outside such that the central area of the tubular body forms a T-shaped configuration for closing the passageway through the filling pipe. The forward end of the tubular body is forced outwards from the outlet or filling opening in form of a bubble to keep this space free from material. A drawback of this filling pipe is its complicated structure for preventing an outflow of material after terminating the filling process.